Clean and wash the vegetables. Cut broccoli and cauliflower into small florets. Cut kohlrabi and parsley root into sticks. Cut carrots into slices. Score the Brussels sprouts stem base crosswise.
Cook the cauliflower and Brussels sprouts in plenty of boiling salted water for about 14 minutes. Add broccoli, carrots and parsley root 10 minutes before the end of cooking time. Add the sugar snap peas 2 minutes before the end of the cooking time.
In the meantime, place the puff pastry slices next to each other and let them thaw at room temperature for about 15 minutes. Wash parsley, dab dry and chop finely. Pour vegetables into a sieve and drain well.
Mix drained vegetables, crabs and parsley. Season with salt, pepper and nutmeg. Pour into a lightly oiled ovenproof dish. Drizzle with olive oil. Place puff pastry slices on top of each other and roll out on a floured work surface 3-4 cm larger than the tin.
Brush the edge of the dough with egg yolk. Cut out 1 small hole from the dough. Place the dough on the casserole dish and press the rim firmly. Bake in the preheated oven (electric oven: 200 °C/ gas: level 3) for 18-20 minutes.
Remove from the oven, serve immediately and garnish with parsley as desired.